Plastic waste is currently generated at a rate approaching 400 Mt [mega-tonnes] / year. The amount of plastics accumulating in the environment is growing rapidly, yet our understanding of its persistence is very limited."

[Source ACS Sustainable Chem. Eng below]

Microplastic pollution - which can now be detected in every environment across the entire planet - includes particles of polyethylene terephthalate (PET), high, low, and linear-low density polyethylene (HDPE, LDPE, and LLDPE), polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS). as well as styrene-butadiene from car tyres, acrylics from paints and dozens of others.

There are three major unknowns regarding the accumulation of microplastic and nanoplastic debris in the environment :

• The first is the scale of the problem. Although the quantity of plastic materials produced each year can be fairly accurately gauged, and the amount that is discarded can also be estimated (as the paper quoted above states) the total amount which ends up as microplastic in the environment is only very roughly quantified.

Plastic debris in the marine environment is widely documented, but the quantity of plastic entering the ocean from waste generated on land is unknown.

Source : Science, Vol. 347, Issue 6223, pp. 768-771 [archived]

• The second unknown is the length of time that the particles take to degrade. It strongly depends on the type of plastic. Some have a half-life of roughly 10 years, others are measured in hundreds, even thousands of years. In addition, much of the mechanical degradation simply results in a larger number of smaller particles. See : Degradation Rates of Plastics in the Environment ACS Sustainable Chem. Eng. 2020, 8, 9, 3494–3511. ( A further complication is the vast array of chemical breakdown products, See Environmental plastic degradationplugin-autotooltip__plain plugin-autotooltip_bigEnvironmental plastic degradation

Of the (estimated) 300 - 400 million tonnes of plastic produced worldwide every year, only around 20% is currently recycled or incinerated. Much of the remaining 80% eventually ends up in the environment.

In the environment, plastics are degraded by weathering, UV light, abrasion, and mechanical action etc - but they are also degraded by microbes (e.g. )

• Thirdly, the biological effects of microplastics on the health of organisms is very poorly researched. It's now known that almost all organisms (so far tested) can and do absorb the particles by eating, breathing and absorbing, but the medium and long-term biological implications for most species are almost entirely unknown.

For the debate about possible human-health effects see Microplastics and human health implicationsplugin-autotooltip__plain plugin-autotooltip_bigMicroplastics and human health implications

Note: Microplastic pollution is so widespread that it's now been found contaminating almost all multicellular lifeforms which have been tested. This article is only related to possible risks to human health.

Further reading : Wikipedia

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